EP2348527A1 - Method for annealing a structure - Google Patents

Abstract

The method involves annealing a composite heterostructure under oxidizing atmosphere, to form an oxide layer (310). The oxidized heterostructure is rotated at a determined angle (theta1) ranging between 40 and 90 degrees, with respect to a support (312) for displacing the oxidized heterostructure on the support to a position in which non-oxidized contact zones (314) between the heterostructure and the support in another position are exposed. The oxidized heterostructure is annealed in the former position under oxidizing atmosphere. An independent claim is also included for a method for fabricating a heterostructure.

Description

The present invention relates to the field of annealing under oxidizing atmosphere used in particular when producing structures or multilayer semiconductor substrates (also called "multilayer semiconductor wafers") obtained by transfer of at least one layer on a support such as structures of the BSOI type ("Bonded Silicon On Insulator").

An example of a known manufacturing process of a multilayer structure is described with reference to Figures 1A to 1F .

As represented in Figures 1A and 1B a composite structure 100 is formed by assembling a first plate 101 with a second plate 102, for example made of silicon. The first and second plates 101 and 102 here have the same diameter. They could, however, have different diameters.

An additional layer (not shown) of the oxide layer type may be formed on one or both plates 101 and 102 before contacting them, particularly in the case of the manufacture of an SOI type structure ( in English " Silicon on Insulator").

The first plate 101 has a chamfered edge, namely an edge comprising an upper chamfer 104 and a lower chamfer 105.

The role of these chamfers is to facilitate the handling of the plates and to avoid breakage of edges that could occur if these edges were protruding, such breaks being sources of particle contamination of the surfaces of the plates.

In the example described here, the assembly of the plates is performed by the molecular adhesion technique well known to those skilled in the art.

Once the bonding step has been performed, the composite structure 100 undergoes a stabilization anneal which is intended to reinforce the bonding between the first plate 101 and the second plate 102 and to cover them with a protective oxide layer.

For this purpose, the stabilization annealing is carried out under an oxidizing atmosphere so as to form an oxide layer 110 over the entire exposed surface of the composite structure 100 ( figure 1C ). Layer Thus, an oxide layer 100 forms a protective layer which makes it possible to protect the composite structure from chemical attack, especially during the subsequent treatment operation.

The structure 100 is then trimmed, which consists mainly of eliminating an annular portion of the layer 106 comprising the chamfer 105 (FIG. Figures 1D and 1E ).

The realization of such a trimming is necessary because the presence of the chamfer 105 prevents good contact between the first and the second plate at their periphery. There is therefore a peripheral zone on which the transferred layer is little or not adhered to the second plate. This peripheral zone of the transferred layer must be removed because it is likely to break in an uncontrolled manner and contaminate the structure with unwanted fragments or particles.

It is preferable to proceed with a so-called mixed trimming, which consists in carrying out a first trimming step by action or entirely mechanical machining ( figure 1D ), followed by a second at least partially non-mechanical trimming step on the remaining thickness of the first plate ( figure 1E ). This second trimming step generally corresponds to a selective chemical trimming with respect to the oxide layers formed on the plates 101 and / or 102. The mixed trimming notably makes it possible to avoid the problems of chipping both at the level of the bonding interface between the transferred layer and the second plate only in the transferred layer itself.

In the example envisaged here, the step of chemical clipping consists in carrying out a chemical etching, also called wet etching. The chemical etching solution is chosen according to the material to be attacked. In this example, using the TMAH or KOH etching solution well known to those skilled in the art, this solution in particular allowing the etching of silicon.

The first plate 101 can then be thinned to form a transferred layer 106 of a determined thickness e ( figure 1F ). This thickness e can reach for example about 10 microns.

Oxidation of the composite structure 100 ( figure 1C ) before the clipping operation makes it possible to prevent the second plate 102 from being etched chemically by the TMAH solution during the chemical trimming step. The oxide layer 110 also allows to protect the surface of the first plate 101 from the clipping chemical attack, before its thinning.

The applicant however observed the appearance of defects in the edges of the composite structures obtained after the chemical trimming step.

More specifically, the defects observed are in the form of scratches distributed over the edges (or slice) of the second plate of the composite structures.

These scratches are undesirable for the manufacturer since they may, for example, be the source of breakage from the second plate, these breakages being likely to contaminate the exposed surface of the first plate. More generally, these defects show a non-optimized manufacturing process, which decreases the attractiveness of the multilayer structures thus produced. These defects can also cause various problems when performing additional technological steps on these defective composite structures (for example, during the manufacture of microcomponents on the exposed surface of the first plate).

However, there is a need to achieve composite structures without such defects, even when the manufacturing process of these structures comprises one or more stages involving chemical attacks. Such chemical attacks may occur in particular, but in a non-exhaustive manner, during a trimming operation or a step of thinning the first plate.

Object and summary of the invention

• une étape de déplacement de la structure oxydée sur le support dans une seconde position dans laquelle la ou les zones de contact entre la structure et le support dans la première position sont exposées ; et
• une deuxième étape de recuit de la structure dans la deuxième position sous atmosphère oxydante.

For this purpose, the invention provides a method of annealing a structure comprising at least one plate, the annealing process comprising a first step of annealing the structure in an oxidizing atmosphere so as to form an oxide layer on at least one a part of the exposed surface of the structure, the structure being in contact with a support in a first position, characterized in that the method further comprises:

• a step of moving the oxidized structure on the support in a second position in which the contact zone or zones between the structure and the support in the first position are exposed; and
• a second step of annealing the structure in the second position under an oxidizing atmosphere.

The annealing process of the invention is particularly applicable to multilayer structures. As indicated above, multilayer structure means a structure made by transferring at least a first plate onto a second plate (or support), such as, for example, the BSOI type structures.

The annealing process of the invention also applies to a single plate, which can subsequently be assembled to one or more other plates.

The method according to the invention makes it possible to grow an oxide layer on the zone or zones of the structure that were in contact with the support during the first annealing step. This is possible because the areas of the structure that were in contact with the support during the first annealing step are discovered (i.e. are no longer in contact with the support) once the structure is disposed in the second position. In this way, a uniform oxide layer is formed over the entire exposed surface of the substrate (s) subjected to the annealing process according to the invention.

This oxide layer can protect the structure of subsequent chemical attacks that can be made on the structure.

For example, this oxide layer effectively protects the structure of chemical attacks that can be implemented during a thinning or trimming operation on all or part of the structure.

The oxide layer thus formed also makes it possible to protect the structure of the chemical attacks implemented during a chemical treatment operation on all or part of the structure.

Thus, the annealing method makes it possible to prevent the formation of scratches on the structure, and in particular on its edges, during a chemical attack.

The support may correspond, for example, to a plurality of holding elements to maintain the structure in position.

In a particular embodiment, no treatment is performed on the structure between the first annealing step and the second annealing step. By this document is meant by "treatment" any technological step intended to modify the characteristics of said structure. Such a technological step can involve, for example, a chemical etching, a deposit of materials, a doping ...

In this variant, the displacement step is the only operation performed on the structure between the first annealing step and the second annealing step. This embodiment makes it possible in particular to ensure the correct positioning of the structure during the second annealing step.

On the other hand, the moving step may comprise rotating the structure at a given angle with respect to the support so that all areas of the structure in contact with the support during the first annealing step are no longer in position. contact with the support at the end of the moving step.

In this way, it is possible to grow an oxide layer on all areas of the structure that were in contact with the support during the first annealing step. This oxide layer is advantageous in that it protects the entire structure of chemical attacks that can be implemented later. It is thus possible to avoid the formation of scratches on the surface of the structure when a chemical attack is subsequently implemented.

The angle of rotation of the structure during the moving step may be, for example, between 40 and 90 degrees.

The invention also relates to a first method for producing a heterostructure comprising a step of bonding a first plate to a second plate, characterized in that the method further comprises annealing the heterostructure according to the defined annealing method. in one of the embodiments mentioned above.

The first method of producing a heterostructure makes it possible to produce a heterostructure comprising a first and a second plate, and this while avoiding the formation of scratches on the second plate during the chemical trimming step.

In particular, this method avoids the formation of scratches at the edges of the second plate.

The annealing carried out on the heterostructure is preferably carried out in such a way that all the zones of the second plate in contact with the support during the first annealing step are no longer in contact with the support at the end of the step. of displacement. In this way, a protective oxide layer is formed on the entire outer surface of the second plate, this oxide layer to protect the second plate of chemical attacks that can be implemented later.

• une étape d'amincissement de la première plaque, et
• une étape de détourage chimique de la première plaque.

Moreover, at least one of the following steps can be performed after the annealing of the heterostructure:

• a step of thinning the first plate, and
• a step of chemical clipping of the first plate.

Here is meant by chemical clipping, a clipping operation using at least one chemical etching

The invention further relates to a second method of producing a heterostructure comprising a step of bonding a first plate to a second plate, characterized in that the method further comprises, before the bonding step, the annealing of the second plate according to the annealing method defined in one of the embodiments mentioned above.

This method of producing a heterostructure makes it possible to form an oxide layer on the surface of the second plate, this layer offering effective protection to the second plate with respect to chemical attacks.

The second method may further comprise, before the bonding step, a step of forming at least one microcomponent in the first plate.

This method is advantageous in that the first plate does not undergo the first and second annealing steps. In this way, the pre-formed components in the first plate are not damaged during the first and second annealing steps.

The second method of producing a heterostructure may further comprise a step of stabilization annealing or reinforcement of the bonding interface of the heterostructure.

This annealing step of stabilizing or reinforcing the bonding interface makes it possible to reinforce the bonding between the first plate and the second plate.

• une étape d'amincissement de la première plaque ; et
• une étape de détourage chimique de la première plaque.

Moreover, at least one of the following steps can be performed after this annealing of stabilization or reinforcement of the bonding interface:

• a step of thinning the first plate; and
• a step of chemical clipping of the first plate.

The oxide layer formed on the second plate thus serves as protection vis-à-vis chemical attacks implemented in particular during the subsequent stages of thinning and / or chemical clipping.

Brief description of the drawings

• les figures 1A à 1F sont des vues schématiques d'un procédé de recuit de stabilisation connu de l'art antérieur ;
• les figures 2A à 2C illustre de manière schématique le mécanisme de formation d'égratignures sur les bords d'une hétérostructure au cours de son procédé de fabrication ;
• les figures 3A à 3D représentent de manière schématique un premier procédé de réalisation d'une hétérostructure selon l'invention ;
• la figure 4 représente, sous forme d'un organigramme, les étapes du premier procédé de réalisation d'une hétérostructure illustré aux figures 3A à 3D ;
• les figures 5A à 5E représentent de manière schématique un deuxième procédé de réalisation d'une hétérostructure selon l'invention ; et
• la figure 6 représente, sous forme d'un organigramme, les étapes du deuxième procédé de réalisation d'une hétérostructure illustré aux figures 5A à 5C.

Other features and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate an example embodiment. In the figures:

• the Figures 1A to 1F are schematic views of a stabilization annealing process known from the prior art;
• the FIGS. 2A to 2C schematically illustrates the mechanism for forming scratches on the edges of a heterostructure during its manufacturing process;
• the Figures 3A to 3D schematically represent a first process for producing a heterostructure according to the invention;
• the figure 4 represents, in the form of a flowchart, the steps of the first method of producing a heterostructure illustrated in FIGS. Figures 3A to 3D ;
• the FIGS. 5A to 5E schematically represent a second method of producing a heterostructure according to the invention; and
• the figure 6 represents, in the form of a flowchart, the steps of the second method of producing a heterostructure illustrated in FIGS. FIGS. 5A to 5C .

Detailed description of an embodiment

The present invention applies, in general, to the realization of annealing in several stages on a structure comprising at least one plate.

The plate or plates forming the structure are generally in the form of slices or "wafers" with a generally circular contour and may have different diameters, in particular diameters of 100 mm, 200 mm or 300 mm. However, it can also be plates of any shape, such as a rectangular plate, for example.

A composite structure or heterostructure is produced by gluing a first plate to a second plate constituting the support of the first plate.

As indicated above, the applicant has observed the appearance of scratches on the edges of the composite structures having undergone chemical attack such as during a trimming or thinning using a chemical phase, and this while the structure was previously subjected to standard stabilization annealing under oxidizing atmosphere. These scratches have been observed in particular on the edges of the second plate of the composite structures.

A thorough study of these scratches has made it possible to highlight the mechanism of formation of these defects and to develop a method to prevent their formation.

The mechanism causing these defects is now described with reference to FIGS. 2A to 2C .

We consider, in relation to the Figure 2A , an example of a composite structure similar to that described in Figure 1B , namely a composite structure 200 formed by assembling a first plate 201 on a second plate 202.

Preferably, at least one of the two plates 201 and 202 has been oxidized before bonding. This oxidation makes it possible in particular to have an oxide layer sandwiched between the two plates once the bonding has been performed. In the example described here, the first plate 201 is oxidized before bonding, so as to form an oxide layer (not shown in the figures) over the entire surface of the first plate.

In the example described here, the two plates are made of silicon and the assembly of the plates is performed by the molecular adhesion technique well known to those skilled in the art. Other bonding techniques can however be used, such as anodic bonding, metallic bonding, or adhesive bonding.

As a reminder, the principle of molecular bonding is based on the direct contact of two surfaces, that is to say without the use of a specific material (glue, wax, solder, etc.). Such an operation requires that the surfaces to be bonded are sufficiently smooth, free of particles or contamination, and that they are sufficiently close together to allow initiation of contact, typically at a distance of less than a few nanometers. In this case, the attractive forces between the two surfaces are high enough to cause the molecular adhesion (bonding induced by the set of attractive forces (Van Der Waals forces) of electronic interaction between atoms or molecules of the two surfaces to be bonded. ).

Furthermore, the first plate 201 has a chamfered edge, namely an edge comprising an upper chamfer 204 and a lower chamfer 205. Figure 2A the plates have rounded chamfers. However, the plates may have chamfers or edge-shaped of different shapes such as a bevel shape.

The Figure 2B schematically represents the composite structure 200, seen from the side of the first plate 201. The position mark "A" shown at the edge of the first plate 201 corresponds, for example, to a flat or a test pattern.

The composite structure 200 is disposed on a support 212 (sometimes called nacelle) in order to carry out standard annealing in an oxidizing atmosphere. This is a stabilization annealing which aims to enhance the bonding between the first plate 201 and the second plate 202 and form a protective oxide layer.

In this example, the carrier 212 includes four holding members 212A, 212B, 212C, and 212D configured to maintain the composite structure 200 in position. The holding elements are in contact with the edges (or the edge) of the composite structure 200, and more particularly, in contact with the edges (or the edge) of the second Plate 202. The portions of the wafer of the second plate 202 in contact with the holding elements are designated respectively by the contact areas 213A, 213B, 213C and 213D (and collectively referred to as contact areas 213).

The composite structure 200 and its support 212 are placed in a furnace or other equipment suitable for annealing (not shown in the figures). Stabilization annealing is performed on the composite structure 200 at a temperature T1 of, for example, between 900 ° C and 1200 ° C, typically at 1100 ° C for two hours.

Annealing provides an oxide layer on the exposed surface of the first plate 201 and the second plate 202.

A step of mixed trimming of the first plate 201 is then carried out, as described with reference to Figures 1D and 1E . In the example described here, the mixed trimming includes a first step of mechanical partial trimming using a grinding wheel or a blade, followed by a step of selective chemical etching of the first plate, using of a TMAH attack solution.

This clipping operation makes it possible to eliminate the portion of the first plate 201 in excess on the edges, without damaging the second plate 202. The preservation of the second plate 202 is possible because the oxide layer (not shown) interspersed between the two plates serves as a stop layer during chemical etching. Chemical etching is thus interrupted at the periphery of the first plate 201 at the level of the oxide layer located at the bonding interface between the two plates.

Once the trimming has been performed, it is possible to thin the first plate 201 so as to form a transferred layer 206 with a thickness e determined, for example, about 10 microns.

Thinning is performed using a grinding wheel or any other tool able to mechanically use the material of the first plate ("grinding" in English).

The Figure 2C schematically shows the structure 200 once stabilization annealing, mixed trimming and thinning performed.

The Applicant has found the appearance of scratches 214A, 214B, 214C and 214D (collectively 214) at the edge of the second plate 202 after the TMAH etching. The distribution of these defects along the edge of the second plate 202 corresponds to the locations of the contact zones 213 mentioned above.

In fact, during the stabilization annealing of the composite structure 200, an oxide layer (of SiO ₂ , in the present example) is formed over the entire exposed surface of the composite structure 200, with the exception of 213. Indeed, during the stabilization annealing, the holding elements 212A to 212D locally mask the edge of the second plate 202 so that the contact areas are not covered by an oxide layer.

To this phenomenon of masking can be added another phenomenon, namely the deterioration of the oxide that may be present on the structure at the contact points (tearing, scratching during removal or other movements of the plate, etc. ). The holding elements 212 may in fact locally damage the preliminary oxide layer formed on the first plate 201 (or possibly on the second plate 202) before bonding and / or the oxide layer forming in the vicinity of the contact points 213 during stabilization annealing.

The contact zones 213 of the second plate 201 being devoid of a protective oxide layer, they undergo directly the chemical etching action of the TMAH solution during the thinning step and / or chemical clipping . The chemical etching at the contact areas 213 then generates the scratches 214. The scratches 214A, 214B, 214C and 214D have thus been observed on the second plate 202 at the locations of the contact areas 213A, 213B, 213C and 213D, respectively. The larger the zones not protected by oxide, the greater the etching effect of the TMAH solution.

These surface defects generated on the edge of the second plate 202 are detrimental for the reasons already mentioned above.

For this purpose, the present invention proposes to perform a multi-step annealing, with displacement of the structure on the support between two consecutive annealing steps, so as to avoid the appearance of these scratches, especially at the edge (or edges) of the second plate.

A particular implementation of the annealing process and a first method of producing a heterostructure according to the invention are now described with reference to the Figures 3A to 3D and 4.

As illustrated in figure 3A the first plate 301, having an upper chamfer 304 and a lower chamfer 305, is first adhered to a second plate 302, which also has chamfered edges, so as to form a composite structure 300 (step E1).

In the example described here, the first and second plates 301 and 302 are made of silicon. The plates can however be made of other materials.

The first plate 301 and / or the second plate 302 may further, and preferably, be covered, before bonding, with an oxide layer (not shown in the figures), in the context, for example, of the manufacture of multilayer structures of the BSOI type.

In the example described here, the assembly of the plates is achieved by molecular adhesion. However, as indicated above, other types of bonding can be envisaged.

The figure 3B schematically shows the composite structure 300, seen from the side of the first plate 301. The position marker "B" shown at the edge of the first plate 301 corresponds, for example, to a flat or a test pattern.

The composite structure 300 is placed on the support 312. In this first position, the four retaining elements 312A, 312B, 312C and 312D of the support 312 are thus in contact with the contact zones 313A, 313B, 313C and 313D respectively. collectively contact areas 313) of the second plate 302. In this example, the contact areas 313 are distributed along the edge of the second plate 302.

However, it can be envisaged that contact zones are located on the rear face of the second plate 302, for example.

The composite structure 300 and its support 312 are then placed in a furnace or other equipment (not shown in the figures) for performing a first annealing of the composite structure 300 in an oxidizing atmosphere (dry or wet) (step E2).

In this example, the first annealing is carried out at a temperature T2 of between 1000 ° C. and 1200 ° C. This first annealing serves as stabilization annealing for the composite structure 300 since it makes it possible to reinforce the bonding between the first plate 301 and the second plate 302.

This first annealing further allows the growth of an oxide layer 310 on the outer surface of the composite structure 300, and in particular on the outer surface of the second plate 302. Here, the term "outer surface of the second plate , the entire surface of the second plate with the exception of the bonding interface.

This oxide layer is mainly intended to protect the outer surface of the second plate 302 subsequent chemical attacks, especially during chemical trimming operations and / or thinning of the first plate 301.

In the case of a method for producing a multilayer structure BSOI, the oxide layer 310 thus formed can reach for example approximately 1 μm in thickness.

Once the first annealing step E2 has been performed, the composite structure 300 is extracted from the furnace. An oxide layer 310 is then present on the entire outer surface of the composite structure 300, with the exception of the contact zones 314 distributed along the edge of the second plate 302.

It will be noted that zones of the edge of the first plate may also be in contact with the support during annealing. In this case, these zones are also devoid of protective oxide layer at the end of the first annealing step E2.

As illustrated in figure 3C the composite structure 300 is then displaced on the support by rotation of a given angle θ ₁ of the composite structure 300 with respect to the support 312 (step E3). This rotation can be performed manually or by means of a suitable positioning device (an aligner for example). The composite structure 300 is thus positioned on its support 312 in a second position corresponding to an angular offset of an angle θ ₁ vis-à-vis the first position ( figure 3B ).

Once the rotation is completed, the contact zones 312 of the second plate 302 are no longer in contact with the holding elements 312.

The angle of rotation θ ₁ is therefore chosen as a function of the geometry of the support 312 used, and more particularly, as a function of the arrangement of the holding elements 312A to 312D along the edge of the second plate 302.

In a particular embodiment of the invention, the angle of rotation θ ₁ is between 40 degrees and 90 degrees.

In the example described here in figure 3C , the composite structure 300 is rotated by a rotation angle θ ₁ of about 40 °.

The composite structure 300 and its support 312 are then placed in an oven (or any other suitable equipment) in order to proceed to a second annealing step in an oxidizing atmosphere (dry or wet) (step E4).

This second annealing is carried out at a temperature T3 of, for example, between 900 ° C. and 1200 ° C.

This second annealing step E4 makes it possible to grow an oxide layer at the level of the former contact zones 314 (not oxidized) of the second plate 302. Such an oxidation is possible because the elements holding the support 312 no longer protect the contact zones 314 of the oxidizing atmosphere.

If necessary, this second annealing step also makes it possible to oxidize at the surface the zones of the first plate 301 that were in contact with the support 312 during the first annealing step E2.

Note that it is not necessary to grow an oxide layer as thick as in the first stabilization annealing step. For example, the second annealing step E4 can be configured so as to form a layer of a few hundred nanometers thick on the old contact zones 314.

In the context of a method for producing a multilayer structure of the BSOI type, for example, the second annealing step E4 can be carried out at a temperature T3 = 950 ° C. so as to form a layer of oxide of 500 nanometers approximately at the level of the former contact areas 314.

At the end of the second annealing step E4, an oxide layer is then present on the entire outer surface of the composite structure 300, and in particular on the entire outer surface of the second plate 302 (the slice of the second plate 302 included).

In the example described here, the mixed trimming (step E5) and the thinning (step E6) of the first plate 301 are then carried out ( 3D figure ).

The mixed trimming operation (step E5) comprises a first mechanical trimming step followed by a chemical trimming step, as explained with reference to Figures 1D and 1E .

More particularly, the mechanical trimming step removes the upper chamfered edge 304 from the first plate 301. Once the mechanical trimming is performed, the remaining annular portion on the periphery of the first plate 201 is no longer protected by oxide. This remaining annular portion can then be chemically trimming with a chemical etching solution, this step making it possible to remove the lower chamfered edge 305 from the first plate 301. In the example described here, a TMAH solution is used to etch the silicon from the first plate. Other etching solutions can however be envisaged, these being chosen in particular according to the composition of the first plate to be cut. In some cases, for example, a KOH solution well known to those skilled in the art is used.

The oxide layer 310 makes it possible to effectively protect the entire second plate 302 from the chemical etching carried out during the chemical trimming step, as well as the chemical attacks that can be implemented in other technological steps during the course of the process. the manufacture of the composite structure (especially during the manufacture of microcomponents on the exposed surface of the first thinned plate).

Once the trimming operation has been carried out, thinning of the first plate 301 is carried out analogously to the thinning of the composite structure 200 (step E6). A transferred layer 306 of a determined thickness is thus formed on the second plate 302, this thickness possibly reaching, for example, approximately 10 μm ( 3D figure ). This thickness is measured between the upper face and the lower face of the first plate outside the chamfered edge.

In a variant of this first embodiment, no treatment is performed on the structure 300 between the first annealing step E2 and the second annealing step E4. As indicated above, here "treatment" is understood to mean any technological step intended to modify the characteristics of the structure. In particular, no step of chemical etching, deposition of materials and / or doping is performed on the structure between steps E2 and E4.

In this variant, the displacement step E3 is the only operation performed on the structure 300 between the steps E2 and E4. This variant makes it possible in particular to ensure the correct positioning of the structure 300 during the second annealing step E4.

Another example of an annealing process and a second method of producing a heterostructure according to the invention are now described with reference to FIGS. 5A to 5E and 6.

The Figure 5A represents a first plate 501 and a second plate 502. The first plate 501 differs from the first plate 301 described in FIG. figure 3A in that it further comprises microcomponents 503 at one of its faces. In addition, the first plate 501 is preferably an SOI plate comprising a buried insulating layer (not shown in the figures) corresponding, for example, to a buried layer of silicon oxide or silicon nitride, or alternatively, to a stack of layers of these materials.

The second plate comprises a position marker "C" on the edge of one of its faces.

The term "microcomponents" here means any type of element made of materials different from that of the first plate. These microcomponents correspond in particular to elements forming all or part of an electronic component or a plurality of electronic microcomponents. It may be, for example, active or passive components, simple contacts or interconnections, or even simple cavities.

The first plate may in particular comprise microcomponents in the case of the three-dimensional integration of components technology (3D-integration) which requires the transfer of one or more layers of microcomponents on a final support, or again in the case of circuit transfer, for example in the manufacture of illuminated imagers on the rear face. Of course, when such microcomponents are present, they must be able to withstand the oxidation thermal treatment according to (invention, for example, cavities.

In this second embodiment, the annealing according to the method of the invention is carried out only on the second plate 502.

The steps E11, E12 and E13 thus differ from the steps E2, E3 and E4, respectively, in that only the second plate 502 undergoes a first annealing, followed by a rotation and a second annealing.

More specifically, the second plate 502 is placed on a support ( Figure 5B ) and a first annealing step E11 is carried out under an oxidizing atmosphere of the second plate 502, in a similar manner to the step E2 described above. This first annealing is carried out at a temperature T4.

As illustrated in Figure 5C a displacement step is then carried out by rotation of an angle θ ₂ of the second plate 502 with respect to its support (step E12), in a similar manner to the step E3 described above.

Once the rotation has been performed, a second annealing step E13 of the second plate 502 is carried out under an oxidizing atmosphere, in a similar manner to the step E4 described above. This second annealing is performed at a temperature T5.

At the end of the steps E11 to E13, a protective oxide layer 510 is present on the entire surface of the second plate 502. This oxide layer covers in particular the areas of the second plate 502 which were in contact with the support during the first annealing step E11 ( figure 5D ).

The first plate 501 is then bonded to the second plate 502 (step E14), so that the microcomponents 503 are located at the bonding interface between the two plates ( figure 5E ). The plate 501 may have been provided with a smoothing layer (eg planarized SiO ₂ ) to provide a more suitable contact surface.

In the example described here, the assembly is carried out by the molecular adhesion technique. As explained above, other assembly techniques are however possible.

The second embodiment makes it possible not to subject the microcomponents 503 of the first plate 501 to the first and second anneals of the process of the invention. Indeed, the high temperatures that are used during these anneals are likely to irreversibly damage the microcomponents 503.

In this second embodiment, therefore, there is no protective oxide layer on the outer surface of the first plate 501. The first embodiment also differs from the second embodiment in that an oxide layer is present at the bonding interface between the first plate 501 and the second plate 502.

Once the bonding is completed, the composite structure 500 thus formed undergoes a consolidation annealing which is intended to reinforce the bonding between the first plate 501 and the second plate 502 (step E15). This annealing is performed at a temperature T6 lower than the temperatures T4 and T5 used during the first and second annealing steps E11 and E13. The temperature T6 is chosen in particular so as not to damage the microcomponents 503 of the first plate 501. It can be an annealing between 400 ° C. and 500 ° C. for 30 minutes to 4 hours.

In the example described here, thinning is then carried out (step E16) comprising a first mechanical step (grinding wheel) followed by a selective chemical treatment with respect to the buried insulating layer of the plate 501. An optional step of trimming (E17) of the first plate 501 can then be performed.

The oxide layer 510 makes it possible to effectively protect the entire surface of the second plate 502 from the chemical etchings used, in particular during the thinning and optionally trimming steps.

Moreover, in some cases, it may be necessary to perform more than one displacement step of the composite structure (rotation) to allow the oxidation of all the zones of the second plate and / or the structure which were in contact with the support during the first annealing. This case can occur, for example, when the contact areas represent a significant portion of the slice of the second plate and / or structure.

In a variant of this second embodiment, no treatment is performed on the second plate 502 between the first annealing step E11 and the second annealing step E13. In particular, no step of chemical etching, deposition of materials and / or doping is performed on the second plate 502 between steps E11 and E13.

In this variant, the displacement step E12 is the only operation performed on the second plate 502 between the steps E11 and E13. This variant makes it possible in particular to ensure the correct positioning of the second plate 502 during the second annealing step E13.

According to another implementation of the annealing process of the invention, a first annealing step is first carried out in accordance with step E2 (or E11).

N rotation steps are then carried out (N being an integer greater than or equal to 2), each rotation step being followed by an annealing step similar to the annealing second step E4 (or E13) described above. Each second annealing step is configured to grow an oxide layer on at least a portion of the still unoxidized contact zones.

It can also be envisaged that the step of moving the annealing process of the invention comprises other types of movement of the structure relative to the support, such as displacement by translation for example, which can be combined with a rotation movement.

Claims (9)

A method of annealing a structure comprising at least one plate, said annealing method comprising a first step of annealing said structure under an oxidizing atmosphere so as to form an oxide layer on at least a portion of the exposed surface of said structure said structure being in contact with a carrier in a first position, characterized in that said method further comprises: a step of moving said oxidized structure on the support in a second position in which the contact zone or zones between the structure and the support in said first position are exposed; and a second step of annealing the oxidized structure in said second position under an oxidizing atmosphere. The manufacturing method according to claim 1, wherein the moving step comprises rotating the structure at a predetermined angle with respect to said support. The production method according to claim 2, wherein said angle of rotation of the structure during the moving step is between 40 degrees and 90 degrees. A method of producing a heterostructure comprising a step of bonding a first plate to a second plate, characterized in that said method further comprises annealing said heterostructure according to the annealing method defined in any one of claims 1 at 3. A method of producing a heterostructure according to claim 4, wherein at least one of the following steps is performed after said annealing: a step of thinning said first plate, and - a chemical of said first plate. A method of producing a heterostructure comprising a step of bonding a first plate to a second plate, characterized in that the method further comprises, before said step of bonding, the annealing of said second plate according to the annealing method defined in any one of claims 1 to 3. A method of producing a heterostructure according to claim 6, further comprising, prior to said bonding step, a step of forming at least one microcomponent in the first plate. A method of producing a heterostructure according to claim 6 or 7, further comprising a stabilization annealing step of said heterostructure. A method of producing a heterostructure according to claim 8, wherein at least one of the following steps is performed after said stabilization annealing: a step of thinning said first plate, and a step of chemical clipping of said first plate.

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